Hybrid vehicles and electric ones are each incorporated with a large battery (a main battery) for driving the vehicles per se, and each use an air cooling blower to cool the battery. The large battery must be subjected to a certain cooling not only during driving of the vehicle but also after the vehicle has stopped and an ignition switch thereof has been turned off, depending on the situation thereof immediately before the turning off. Such the cooling blower is controlled in accordance with an instruction received from an electronic control unit, called as an ECU (Electronic Control Unit), which controls a wheel driving unit including an engine. The instruction is made including a cooling capacity (e.g. the rotation number of its fan) and cooling period (e.g. a rotation duration time of the fan) of the cooling blower. However, there is a problem that, when the ignition switch is turned off to halt power supply to the electronic control unit, transmission of the instruction on cooling to the cooling blower is normally halted.
Conventionally, in order to address the problem in a conventional vehicle with an engine, the following technique has been proposed to prevent damage to the engine from overheating. That is, in the technique, there are included a load detecting means for detecting loads of the engine, a cooling water temperature detecting means for detecting the temperature of cooling water of the engine, and a driving means for driving such as an electric cooling pump and an electric cooling fan. Then, after the engine has been halted, the driving means is allowed to operate by supplying electric power for a certain period of time to the driving means, in accordance with the loads of the engine and the temperature of the cooling water, from the battery via a relay or the like without via the electronic control unit (see Patent Literature 1, for example).
However, the conventional technique described above requires additional components, such as interconnections and relays, which are needed for transmitting information to the driving means from the load detecting means, the cooling water temperature detecting means, and the like. Moreover, another method can also be considered in which the electronic control unit is caused to continue to operate by supplying it with electric power even after the engine has been halted, and then the electronic control unit operates a relay by itself to halt the power supplying after a lapse of a certain time from the engine halting. However, this case is expected to also require an additional relay and to suffer from possible failures that, for example, the contacts of the relay would fuse together. Moreover, because the electronic control unit is basically intended to control the wheel driving means, the control unit has a large amount of power consumption. Therefore, use of the electronic control unit for controlling the cooling blower results in an excessive amount of power consumption.